Battery selector switch upgrade?

[Networker]

I put in a 1200AH LiFePO bank last year and left the original battery selector switch alone. It failed this week, it’s 20 years old. Not sure if it was the insane 400 Amps I was running through when cooking with electric stove it or if just old/mechanical/corroded. But it got me thinking when shipping for new ones today.

My question is, the battery bank can push out 800amps continuous, do I need battery selector switch that can handle that load if I were to run that high, or would a switch that can handle 350-400Amps continuous be ok, or should I go to 500-600? I never really thought about this before, curious how to size these switches when having a large battery bank.

Thank you for any help!

[Wotname]

The better quality switches have a max continuous rating, a short term 5 minute rating and a 10 sec (engine starting) rating.

Choose accordingly.

[MARC D]

Defititively go for at least 600 amp switch. Blue Sea has a HD 600 amp that is not too expensive.

[Networker]

Originally Posted by MARC D

Defititively go for at least 600 amp switch. Blue Sea has a HD 600 amp that is not too expensive.

That’s the one I got, the HD series.

[Ninedotsix]

The switched circuit should be protected by an appropriate fuse, that is sized to protect the wire and devices like the switch on the line.

There is another concern, and here I get a little fuzzy on DC specifications, that concern being the "interrupting rating" of the switch.
It means how much current flow can the switch interrupt ("break") without exploding into shrapnel and flames. The short circuit potential for the lithium batteries is huge, and here I presume the wire leading from the batteries is protected.

If it were me, I would send an email to tech support at BlueSeas Systems, or call and ask for tech support, before buying and installing the switch. You will find them very helpful, so be prepared with complete information about wire size, etc.

I learned a lot when installing an electric motor repower and would not have reasoned it out on my lonesome, because it required installation features that I had to become convinced to include, in order to protect the crew and vessel.

Besides the size of fuses, the allowable length of run between the batteries and fuse is important. ABYC guidelines are readily available and cover these aspects.

As applies to most work, I always hear the words: "Now, please explain to the ladies and gentlemen of the jury WHY you decided to do it the way that you did."

Keep Safe and Healthy ~ 9.6

[Networker]

Correct, the wires are protected: 500A ANL on the batteries, 400A ClassT going into the Victron Quattro from batteries, and another 400A ANL coming out of the alternator.

I guess if I only can produce 400A max, that’s the max the wires can take before the fuse blows, the switch wouldn’t need to be more than 500A since the fuses are below that? So if I go with the 600, I guess it’s safe?

Steve

[rondelais]

Lifetime of electrical components is increased dramatically if they are debated - that is, if the actual load is substantially less than their maximum rating. So, I would think that a switch rated at 600A continuous would be pretty reliable and have a reasonable lifetime if actually used below 300A or so. That said, is there any way to split the load among more than a single switch? When I redid my power system, I put separate switches (and fuses) between the battery bank and the heavy loads - one for the main power breaker panel, one for the inverter, and one for the anchor windlass. I am also not a fan of the 1-2-both type of switch. So, I have a small panel in the cabin close to the batteries with a total of six rotary switches - the three mentioned above, plus one for connecting the starting battery to the starter, one connecting the house battery to the starter (if both these are turned on the batteries are paralleled) and one that connects solar to the house batteries. This provides a lot of flexibility, but is easy to manage. I really haven’t thought of any downsides to this approach - any thoughts from the experts out there?

[goboatingnow]

I presume you meant “ derating “

[rondelais]

Yeah, spell check got me again. Derated it is!

[purplesunrise]

We discovered that the original Lagoon switches were inadequate, poorly constructed and were causing a 1 volt drop (12 volt system). At some times the switches were warm to the touch. No switch should ever be warm or hot. New Blue Sea HD switches on both the positive and negative solved the problem. Voltages are back up and the switches never get warm with any load.